1. Field of the Invention
The present invention relates generally to medical apparatus and methods. More particularly, the present invention relates to implantable devices and methods and systems for detecting their dysfunction or impending dysfunction.
Implantable medical devices, particularly those indicated for long term use in the human body, are highly regulated and must meet certain safety requirements. It is known that when a device is implanted in the body, the materials forming the cover and structural elements of the device may degrade and fatigue over time. It is also known that improper or excessive handling during implantation could stress the structural integrity of the device. In devices with movable mechanical parts, the wear and tear of the materials in contact with each other could lead to degradation of the surface, the interior volume, and eventually the structural stability of the part itself. Such wear can also release debris particles which in turn can cause harm in a variety of ways including triggering immune reactions which can cause osteolysis and blocking luminal structures which can cause strokes or bowel obstruction. When large enough, the damaged part of the device could shred healthy cells and tissues from red blood corpuscles to bone. Failure of the structural integrity of the device can cause not only dysfunction but severe injury. Often the wear of the device can be moderated or evened by changes in physical activity. Or the impaired part of the device could be replaced without difficulty before the rest of the device is damaged necessitating more extensive revision procedures and rehabilitation. Not only would this enhance safety and reduce costs, the life of the product can be prolonged. Therefore, it would be desirable to detect, to monitor, or to predict such an event and take measures before any irreparable damage to the device or injury to the patient ensues.
Prosthetic devices implanted in numerous locations in the body are prevalent in medical practice and are expected to be of even greater importance than ever before. With medical advances human longevity has increased the population of elderly needing them. Obesity adds further wear and tear on the body. In today's data driven generation, people are more involved in taking care of their own health. The implications are many. Initial, primary therapeutic procedures are performed at younger ages and revision or replacement procedures are increasingly more common. Device statistical lifecycles are no longer satisfactory as patients need information specific to the device implanted in their own body and individualized counseling. Having a device that can be self monitored economically by the patient would be further helpful and reduce overall healthcare costs.
Many devices, such as cardiovascular valves, have parts that are dynamic when performing their function and cannot be stopped for examination. Thus failure prediction and detection often depend on secondary signs, such as errant flow patterns by imaging such as ultrasound. By the time their function is impaired enough to be detected, the wear and tear to the device has already far progressed to require more urgent treatment. Early detection of partial failure through a direct or primary method would enable more accurate diagnosis and better treatment planning.
Other devices suffer repeated or cyclical stresses from deliberate manipulation or secondary body movement. Devices such as insulin or other drug pumps require refilling of the reservoir, typically through a needle. Repeated stabbing in the same location could induce and propagate these defects in the covering that could allow intrusion of body fluids and impair the precisely calibrated functions. Or the refilled fluid could leak through the defects established or propagated by the injecting device. Electronic stimulation devices, such as neurostimulators, and many mechanically restrictive devices, such as lapbands used in bariatric surgery, require fixation of certain critical components to body tissues. As the device and the body tissues are not isolated from motions of the rest of the body, any movement could cause mechanical stress and, over time, fatigue leading to tears or dislocations of the device.
For these reasons, it would be desirable to provide apparatus and methods to detect, to monitor, or predict an actual or potential breach of a surface, layer, or body of an implantable object or device in the body. Prompt removal and/or replacement of such impaired devices or components thereof could avert many, if not all, of the problems associated with failure of such devices. The methods and apparatus would preferably be adaptable for use in many devices without adversely affecting the device's performance or structural integrity. It would be beneficial if the device could be directly examined while functionally deployed in motion without interfering with its performance, even temporarily. It would be further desirable if the breach of the device were detectable to the patient in an easy, rapid, and reliable fashion at home and in other settings away from the doctor and hospital. Additionally, it would be beneficial if the system were able to monitor the device non-invasively on a frequent basis without incurring significant additional cost for each diagnostic event. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Background Art
U.S. 2006/0111777 and U.S. 2006/0111632 describe inflatable and rigid implants having embedded conductors utilizing transponders to signal a breach. U.S. Pat. No. 5,833,603 describes an implantable transponder that can be used to detect breach or wear in implantable devices. Breast implants and methods for their use are described in U.S. Pat. Nos. 6,755,861; 5,383,929; 4,790,848; 4,773,909; 4,651,717; 4,472,226; and 3,934,274; and in U.S. Publ. Appln. 2003/163197. Gastric balloons and methods for their use in treating obesity are described in U.S. Pat. Nos. 6,746,460; 6,736,793; 6,733,512; 6,656,194; 6,579,301; 6,454,785; 5,993,473; 5,259,399; 5,234,454; 5,084,061; 4,908,011; 4,899,747; 4,739,758; 4,723,893; 4,694,827; 4,648,383; 4,607,618; 4,501,264; 4,485,805; 4,416,267; 4,246,893; 4,133,315; 3,055,371; and 3,046,988 and in the following publications: US 2004/0186503; US 2004/0186502; US 2004/0106899; US 2004/0059289; US 2003/0171768; US 2002/0055757; WO 03/095015; WO88/00027; WO87/00034; WO83/02888; EP 0103481; EP0246999; GB2090747; and GB2139902.